Today, athletes swear by it, trainers tout it and research institutions back it up. But I’m not totally sold.

Why? Of the 25-odd carbo-loading studies I read through which showed improved energy, few actually quantified the improvement. And those that did, well, they reported energy extension ranging from 20%, to a paltry 2-3%.

Which begs: even if carbo-loading techniques do boost glycogen storage—and, in turn, do improve endurance performance—is it enough to make it worth the trouble?

How is gobbling Pasta Carbonara trouble, you ask? Well, let’s take a look at what the classic carbo-loading regimen entails.

Carbo-loading no cakewalk

The standard carbo-loading method calls for total carb depletion before you load. It’s not enough to simply up your carb intake before a big event—before you get to touch that five-pound baked potato, you have to earn it with five days of turkey, beans and protein bars.

Carb-starving yourself induces the muscles to ‘thirst’ for glycogen and in turn store up more than it would otherwise hold, Charla McMillian (author of Boot Camp Abs) explains.

To drain glycogen stores, the classic method begins one week prior to race day with a rigorous workout. On days 2-4, you’ll taper training and eat a low carb diet (roughly 10% of your intake). On days 5-7, you’ll ratchet down your physical activity to a minimum and skyrocket your carb intake—all the way up to 90% of your diet.

Hey, you say. One highly-regimented week doesn’t sound too bad. But how do fatigue, irritability and a weakened immune system sound? According to Joel Maloof, a sports health scientist, even a short period of severe carb depletion can cause all of the above pre-race joys.

Still might be worth it, you think?

Well what if I told you that following the carbo-loading regimen to a ‘T’ is no guarantee it’ll work?

The Australian Institute of Sport also found carbo-loading to be an effective way to boost endurance. The same study found that eating carbs immediately before, during and after a workout can also keep an athlete going for hours. Gee. Why not skip the carb rollercoaster and just munch on cereal and sandwiches all day?

And what about the ladies? Well, I’m glad you ask… because most researchers don’t. The majority of carbo-loading studies use only male participants. Meanwhile, women may be scarfing double the carbs with nothing to show for it.

Apparently carbo-loading in women is a whole ‘nother ballgame. McMaster University conducted two female carbo-loading studies and found that women simply can’t store as much muscle glycogen as men. In fact, in its first study, after a 4-day carbo-loading regimen female participants came away with no glycogen surplus at all. Zilch.

Women might be able to boost our carbo-loading threshold, Baylor University found, if we simultaneously double up on calories. But wait. Does this open up the possibility that the energy boost some female athletes see “with carbo-loading” could actually be influenced by other factors—like eating more calories?

And then there was the University of Helsinki study. It concluded flat-out that carbo-loading doesn’t always cause higher muscle glycogen stores. It’s a crapshoot. (Side note: this was an all-male test group.)

…

If you’re itching to add a few more minutes to your next bike ride, you might give carbo-loading a try. But with results so iffy, and carb math that could make an engineer’s head spin (even with that handy-dandy carbo-loading calculator), then why bother?

Especially if there are simpler ways to keep your energy up—some of which still involve, thank goodness, a big bowl of fettuccini.

2 Comments

This article to which I contributed some background research info) raises interesting questions about carbohydrate loading, gender differences noted in research, and how the trained endurance athlete can improve performance. While most points are well highlighted, unfortunately significant factsand contributing factors have been left out in favor of promoting the author’s preference to keep eating as she wishes and not worry about altering habits to ensure championship performance.
1) the “classic” method of carbo loading with several days of depletion (with risk of irritability, performance impairment mid-training plan, loss of focus, etc.) has long ago been shown unnecessary for effective carbloading. Studies abound showing the same glycogen super-loading occurring with a simple 4 day carb loading phase. These studies include those to which I referred in the research i supplied as well as the articles included in this piece. So there is no need to lament a requirement for nutrient denial before a long endurance event;
2) The few studies indicating a difference between males’ and females’ ability to increase glycogen storage and use for endurance events were ultimately shown incorrect and that theory disproven when scientists a) corrected for the actual carbohydrate theshold required to induce glycogen super-loading in both genders (8-10 g carbohydrate per kg lean bodtweight — earlier researchers for some reason had decided to feed the women significantly less), and b) actually conducted the studies using long endurance exercise (previous studies used submaximal exercise — very hard to extrapolate results about marathon performance when we’ve only tested them on the leg press . . . ) The comparison is well highlighted in the article mentioned from the Journal of the International Society of Sports Nutrition);
3) The performance differences observed – again as mentioned in the more recent studies – in both genders are statistically significant. For the trained athlete, those statistics are important and can mean the difference between stellar performance and going home with nothing. A difference of between 2% and 20% in time to fatigue seems small unless you’re the runner breaking the tape.
Obviously for the amateur athlete simply trying to “survive” a race v. performing at optimal level, the choice to keep the pre-diet nutrition exactly the same as always is much more conveneient thatn trying to feed for optimal performance. That same athlete is likely making similar choices for the rest of his/her training, muscular strength and development, supplementation for recovery and endurance improvement, work on stride length and frequency, etc. But when the highly trained oerformer prepares for the next race, I suggest he or SHE include carb loading in their routine, get it right, and enjoy improved performance.

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